Interval Edge-Colorings of Cartesian Products of Graphs I

Petros A. Petrosyan ; Hrant H. Khachatrian ; Hovhannes G. Tananyan

Discussiones Mathematicae Graph Theory, Tome 33 (2013) no. 3, p. 613.

Résumé

A proper edge-coloring of a graph G with colors 1, . . . , t is an interval t-coloring if all colors are used and the colors of edges incident to each vertex of G form an interval of integers. A graph G is interval colorable if it has an interval t-coloring for some positive integer t. Let [...] be the set of all interval colorable graphs. For a graph G ∈ [...] , the least and the greatest values of t for which G has an interval t-coloring are denoted by w(G) and W(G), respectively. In this paper we first show that if G is an r-regular graph and G ∈ [...] , then W(G⃞Pm) ≥ W(G) + W(Pm) + (m − 1)r (m ∈ N) and W(G⃞C2n) ≥ W(G) +W(C2n) + nr (n ≥ 2). Next, we investigate interval edge-colorings of grids, cylinders and tori. In particular, we prove that if G⃞H is planar and both factors have at least 3 vertices, then G⃞H [...] N and w(G⃞H) ≤ 6. Finally, we confirm the first author’s conjecture on the n-dimensional cube Qn and show that Qn has an interval t-coloring if and only if n ≤ t ≤ [...]

Détail

Classification : 05C15, 05C76
Mots-clés : edge-coloring, interval coloring, grid, cylinder, torus, -dimensional cube